The work described herein consists of experiments designed to elucidate the mechanisms by which estrogen induces the synthesis of vitellogenin, the precursor of the egg yolk phosphoproteins, in rooster liver. Vitellogenin mRNA has been partially purified from rooster liver and has been shown to have a size approximately 2x10 to the 6th power daltons. Vitellogenin mRNA is not present in normal roosters whereas it is synthesized and accumulates in the liver in response to estrogen stimulation. In addition vitellogenin mRNA can be isolated from roosters no longer actively synthesizing vitellogenin after estrogen withdrawal in amounts equal to approximately 30 percent of that found in the fully induced state. Vitellogenin mRNA will be purified to homogeneity and used as a template to synthesize complementary DNA. This DNA will be used to study the synthesis of vitellogenin mRNA in vitro and in vivo.